Regarding measures to reduce the amount of NOx from a gas turbine combustor, it is important to control fuel distribution so as not to generate a locally high fuel concentration, and it is necessary to make the fuel concentration uniform. In order to do so, it is important to increase and uniformize the amount of main air through which the majority of fuel passes.
Previously, a combustor in which the main airflow from a combustor casing is turned by 180 degrees and guided into a main premixing nozzle has been disclosed (for example, see Patent Literature 1). In such a combustor, in order to eliminate uneven flow deflection accompanied by, for example, flow separation, uniform flow and concentration in the combustion region are achieved by disposing a baffle plate at the inlet, changing the number of turning vanes at the turning position to two, or making the distance from the fuel mixing position to the 180-degree turning position sufficiently long for rectifying the flow.